JPS6224945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to semiconductor processing technology, and particularly to a technology for doping silicon with oxygen.

BACKGROUND OF THE INVENTION One of the problems in integrated circuit manufacturing technology is isolating some or all of the various semiconductor devices thereon from a substrate.
A technique currently used to isolate devices from a substrate is diffusion isolation. In that method, isolation is achieved by reverse biasing the underlying region and the forming portion of the device. Dielectric insulation is also used, in which a dielectric insulation layer separates the device from the substrate. Although these techniques provide effective isolation, they have the disadvantage of requiring significant manufacturing time and increasing the manufacturing cost of the device.

Recently, insulation technology using ion implantation technology has been developed. In that technique, a layer in a semiconductor body is heavily implanted with oxygen. The substrate is then heated to an elevated temperature to form a silica substrate layer. This process requires ion implantation for a long period of time, and requires annealing at a relatively high temperature for a long period of time due to significant damage to the crystal. The purpose is to eliminate the drawbacks of the prior art.

Furthermore, it is an object of the invention to develop a method for forming insulating regions in p-type substrates which does not have the disadvantages of conventional methods of this type.

Another object of the invention is to provide a method of this type which is relatively inexpensive and yet allows excellent results to be achieved.

A secondary object of the invention is to provide a semiconductor device having an improved insulating layer or region.

In order to achieve these purposes and such other purposes as may become apparent from the description below.
A method of forming an insulating region in a p-type silicon substrate for isolating at least one semiconductor device from the remainder of the substrate features a doping level substantially corresponding to the doping level of the substrate material in the desired region. implanting oxygen ions into the desired region until the oxygen ions at least compensate for the effects of p-type doped impurities in the desired region, converting the region into a silicon insulating region ranging from intrinsic to n conductivity type; heating the substrate to a temperature sufficient to activate the oxygen ions.

According to another aspect of the invention, a p-type silicon substrate having an active surface, at least one semiconductor device disposed on the active surface, and an intrinsic silicon substrate disposed between the semiconductor device and the remainder of the substrate. A semiconductor structure is provided comprising a silicon insulating region containing oxygen of up to a range of conductivity types.

Oxygen-rich silicon, for example, has a temperature of 430 to 470°C.
It exhibits strong donor activity when heated to a temperature of .
The nature of this effect is not fully understood. However, it is believed that the formation of SiO ₄ complex compounds occurs at some point during the processing. At lower heating temperatures no complexes are formed and therefore no donors are generated. On the other hand, no donor is generated even if heated to a high temperature. If oxygen-rich p-type silicon is heated for a long time, its conductivity type changes to n-type. Before this conductivity type inversion, the oxygen complex donor compensates for the acceptor present in the original p-type material and increases the resistivity of the semiconductor, resulting in the formation of intrinsic silicon.

(Description of Embodiments) The above-mentioned and other objects and features of the present invention will become clearer from the following description with reference to the accompanying drawings.

Referring to the drawings, for example bipolar or
A semiconductor device 11, such as a MOS transistor, is formed on the active surface of a silicon substrate. Prior to the formation of the semiconductor device, an oxygen-rich layer 13 is formed in the substrate by light implantation of oxygen ions. Typically layer 13 is implanted to an oxygen level of 10 ¹⁸ cm ^-3 . A semiconductor device 11 is then formed on the surface of the substrate by standard techniques, and the substrate is subsequently heated to 430°C to 470°C, preferably
It is heated to 450℃ to activate the silicon-oxygen complex, which removes the p-type silicon present in the original p-type silicon.
layer 1 by compensating or overcompensating for the effect of type doping impurities.
A high resistivity or n-type region is formed in the substrate 3 to insulate the semiconductor device 11 from the substrate 12 .

This technique can be used in MOS or bipolar processing when it is required to isolate the semiconductor device from the substrate. Oxygen-free p-type silicon wafers are implanted with oxygen to a depth beyond the deepest point of the semiconductor device structure. Semiconductor devices are then formed in a conventional manner, after which the wafer is activated by heating to 430 DEG -470 DEG C. in an inert atmosphere to provide an insulating layer prior to device metallization. Finally, the wafers are metallized, cut, and packaged into containers to form the final semiconductor devices.

The technology described here is DMOS (double diffused
Particularly suitable for manufacturing MOS) structures. This is because such a structure requires a lightly doped n-type region on a p-type substrate. Typically such structures are achieved by growing epitaxial layers on a substrate at high temperatures. However, the use of such high temperatures involves associated problems of wafer distortion and layer thickness control. The technique of the present invention substantially solves these problems by using relatively low temperatures.

For example, if oxygen ions are implanted into a p-type floating region substrate (containing no oxygen) and subsequently annealed, the oxygen donor reverses the conductivity type of the semiconductor surface and an n-type layer is formed. . The resistivity of this layer can be controlled by a corresponding adjustment of the annealing period. Furthermore, if oxygen ions are implanted through a mask into the planned active region, then lateral isolation is also achieved at the same time. This eliminates the need for conventional diffusion/driving processes.

Figure 2 shows a typical DMOS structure. This structure can be fabricated using the oxygen ion implantation techniques described herein. The device can be formed in an oxygen-free p-type substrate. As shown, the device has the usual source S, gate G, and drain D regions, isolated from the substrate by an n ^- region. The n ^- region is typically 1 μm deep and is formed by ion implantation of oxygen followed by annealing at a temperature of 430-470° C. to activate the oxygen donor centers. Typically such a layer has a beam intensity of 5 x 10 ¹³ cm
^-2 , can be obtained by implantation of doubly charged oxygen ions with an energy of 200 KeV, whereby 1 μ
An oxygen peak concentration of 10 ¹³ cm ^-3 is given at a depth of m,
It is then annealed at 450°C for 1000 minutes. The oxygen ion energy and concentration are of course selected depending on the desired n-type layer doping level, and the annealing time is selected to obtain the optimum donor concentration.

The inventive technique described above is clearly not limited to the manufacture of discrete devices, but can of course also be effectively applied to the manufacture of integrated circuits.

Although the principle of this invention has been explained above in relation to a specific device, it should be understood that this is merely an example and does not limit the technical scope of this invention as set forth in the claims. Make a clear statement.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor device formed in a silicon substrate and insulated from the substrate by a high resistivity layer, and FIG. 2 is a cross-sectional view of a DMOS structure insulated by an oxygen ion implantation layer. It is. DESCRIPTION OF SYMBOLS 11... Semiconductor device, 12... Base, 13... Oxygen ion implantation layer, S... Source, D... Drain, G... Gate.

Claims (1)

[Scope of Claims] 1. A p-type silicon substrate having an active surface, at least one semiconductor device disposed on the active surface, and an oxygen disposed between the semiconductor device and the remainder of the substrate. A semiconductor structure consisting of an insulating region of silicon ranging from intrinsic to n conductivity type containing as a doped impurity. 2. The semiconductor structure according to claim 1, wherein the semiconductor device has a DMOS configuration. 3. The semiconductor structure of claim 1, wherein the insulating region extends to a depth of 1 μm from the active surface. 4. The insulating region is produced by implanting oxygen ions and heating the substrate to a temperature at which the oxygen ions become activated and compensate for the effects of doped impurities in the insulating region. The semiconductor structure described. 5. implanting oxygen ions in a layered manner into a desired region of the substrate at a concentration level substantially corresponding to the doping level of the substrate material; The substrate is heated for a period of time sufficient to convert it into layered separated regions.
heating to a temperature in the range of 430°C to about 470°C. How to form. 6. The method of claim 5, further comprising the step of masking selected areas of the substrate during at least a portion of the ion implantation step. 7. The method of claim 5, wherein a substantially oxygen-free substrate is used before said ion implantation step is performed. 8. The method of claim 5, wherein the implantation step bombards the substrate with oxygen ions at an energy of 200 KeV to provide a peak oxygen concentration of 10 ¹⁸ cm ^-3 at a depth of 1 μm. 9. implanting oxygen ions in a layer into a p-doped silicon substrate at a concentration level substantially corresponding to the doping level of the substrate; forming one or more semiconductor devices in said substrate; , converting the layered region into which oxygen ions are implanted into an intrinsic or n-conductivity type region;
In order to separate the above-described semiconductor devices, the substrate is heated at a temperature of about 430° C. to about 470° C. so as to activate oxygen in the region into which oxygen ions are implanted into the layered region and compensate for at least the effect of the p-type impurity in this layered region. A method for forming a semiconductor structure, comprising the step of heating to a temperature in the range of .degree. 10. The method of claim 9, further comprising the step of masking selected areas of the substrate during at least a portion of the ion implantation step. 11. The method of claim 9, wherein a substantially oxygen-free substrate is used before said ion implantation step is performed. 12. The method of claim 9, wherein said implantation step bombards the substrate with oxygen ions at an energy of 200 KeV to provide a peak oxygen concentration of 10 ¹⁸ cm ^-3 at a depth of 1 μm.